Synthesis and anti-HIV activity of alkylated quinoline 2,4-diols

Article abstract of DOI:10.1016/j.bmc.2010.03.015

Naturally occurring quinolone alkaloids, buchapine (1) and compound 2 were synthesized as reported in literature and evaluated for anti-HIV potential in human CD4+ T cell line CEM-GFP, infected with HIV-1_NL4.3 virus by p24 antigen capture ELISA

Full text of DOI:10.1016/j.bmc.2010.03.015

Bioorganic & Medicinal Chemistry 18 (2010) 2872–2879
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis and anti-HIV activity of alkylated quinoline 2,4-diols
a
Nafees Ahmed a, Keyur G. Brahmbhatt a, Sudeep Sabde b, Debashis Mitra b, , Inder Pal Singh ,
*
Kamlesh K. Bhutani a,
*
a Department of Natural Products, National Institute of Pharmaceutical Education and Research (NIPER), Sector 67, S.A.S. Nagar, Mohali 160062 Punjab, India
b National Center for Cell Science (NCCS), Pune University Campus, Ganeshkhind, Pune 411007 Maharashtra, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Naturally occurring quinolone alkaloids, buchapine (1) and compound 2 were synthesized as reported in
literature and evaluated for anti-HIV potential in human CD4+ T cell line CEM-GFP, infected with HIV-
1NL4.3 virus by p24 antigen capture ELISA assay. The compounds 1 and 2 showed potent inhibitory activity
with IC50 value of 2.99 and 3.80 lM, respectively. Further, 45 alkylated derivatives of quinoline 2,4-diol
were synthesized and tested for anti-HIV potential in human CD4+ T cell line CEM-GFP. Among these, 13
Received 14 January 2010
Revised 7 March 2010
Accepted 9 March 2010
Available online 12 March 2010
derivatives have shown more than 60% inhibition. We have identified three most potent inhibitors 6, 9
and 23; compound 6 was found to be more potent than lead molecule 1 with IC50 value of 2.35 lM
and had better therapeutic index (26.64) as compared to AZT (23.07). Five derivatives 7, 19a, 19d, 21
and 24 have displayed good noticeable anti-HIV activity. All active compounds showed higher CC50 val-
ues which indicate that they have better therapeutic indices.
Keywords:
Quinoline 2,4-diol
Alkylation
Anti-HIV activity
CEM-GFP cells
Ó 2010 Elsevier Ltd. All rights reserved.
1. Introduction
mechanism.3 HIV infection represent a global health hazard neces-
sitating identification of novel targets and new lead molecules for
Acquired immunodeficiency syndrome (AIDS) is one of the
greatest challenges to mankind in the history of Biomedical Sci-
ence. It is estimated that 33.4 million people were living with
HIV, 2.7 million became newly infected and 2.0 million lost their
lives as a result of AIDS (UNAIDS 2009 Report).1 Two major types
of HIV have been identified, HIV-1 and HIV-2. HIV-1 is the cause
of worldwide epidemic of AIDS whereas HIV-2 is less pathogenic
and found mostly in West Africa. HIV-1 is classified into three ma-
jor groups M, O and N (non-M and non-O). There are ten subtypes
within group M from subtype A to subtype K, of which presently
subtype C is most prevalent worldwide. Group O contains distinct
group of heterogeneous viruses. Group N viruses exhibit distinct
sequence of envelop protein from group M and group O. HIV-1
causes loss of CD4+T cells by direct killing of the cells or indirectly
by impairing function of cells consequently leading to the cell
destruction by apoptosis.2 Though successful use of synthetic Re-
verse Transcriptase (RT) inhibitors and protease inhibitors in com-
bination (Highly active antiretroviral therapy, HAART) have
effectively suppressed the virus replication and significantly pro-
longed the life of AIDS patients, the appearance of mutant viruses
that are resistant to current drugs require the development of new
types of anti-HIV drugs, from the point of view of structure and
drug discovery.4 Therefore, there is an urgent need to develop new
compounds with potent anti-HIV activity and with novel modes of
action.
Natural Products are an important source of new drug candi-
dates. Many natural products, semi-synthetic or NP derived candi-
dates having variety of biological activities are in clinic or in
clinical trials.5 Anti-HIV agents from natural resources belonging
to several classes including terpenoids, coumarins, alkaloids, poly-
phenols, tannins and flavonoids have been elaborately reviewed by
our group.6 Bevirimat, a semi-synthetic derivative of the plant
metabolite betulinic acid, is in Phase IIb trials in HIV-infected pa-
tients.5 Bevirimat blocks HIV maturation by inhibiting the final
step of the HIV Gag protein processing.7 Batzelladines,8 harmine,9
michellamine B,10 calanolide A and B, calceolarioside B,11 mallotoj-
aponin,12 macrocarpals13 are few other examples of anti-HIV natu-
ral products. The buchapine (1), quinolone alkaloid, was isolated
from methanolic extract of the epigeal part of Haplophyllum
bucharicum,14 Haplophyllum. tuberculatum15 and Euodia roxburghi-
ana.16 Compound 2 was also isolated from H. tuberculatum and
CH2Cl2/MeOH (1:1) extract of E. roxburghiana along with 1. The
natural products 1 and 2 (Fig. 1) exhibit anti-HIV activity against
HIV-1 in cultured human lymphoblastoid CEM-SS cells (EC50
0.94 lM, IC50 29.0 lM and EC50 1.64 lM, IC50 26.9 lM), respec-
tively.16 These molecules are not yet explored in order to obtain
the new lead molecules for anti-HIV activity. As a part of our ongo-
ing work to identify newer anti-HIV agents,17 we selected natural
products 1 and 2 for our study. Here, we report synthesis and
* Corresponding authors. Tel.: +91 1722232208; fax: +91 1722232208 (K.K.B.);
tel.: +91 2025708151; fax: +91 2025692259 (D.M.).
E-mail addresses: dmitra@nccs.res.in (D. Mitra), kkbhutani@niper.ac.in (K.K.
Bhutani).
0968-0896/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2010.03.015

N. Ahmed et al. / Bioorg. Med. Chem. 18 (2010) 2872–2879
2873
step by heating with lithium hydroxide and excess of alkyl halides
in water at 80 °C. Alkylation in polar protic solvent like water gives
more C/O selectivity. After optimization, this method was very effi-
cient for di-alkylation by using lithium hydroxide as base in water.
The products were obtained in good 60–80% yields.21
Figure 1. Anti-HIV natural products.
2.1.2. Series 2
The compounds 19a–e were synthesized based on natural prod-
uct 2 as illustrated in Scheme 3. The C-3 alkyl quinoline 2,4-diol
derivatives (18a–e) were obtained by treatment of 3 with alkyl ha-
lides and LiOH in water at 80 °C in 50–70% yield. The 18a–e were
then refluxed with alkyl halides and acetone containing anhydrous
K2CO3 to yield C-3, O-4 di-alkyl quinoline 2,4-diol derivatives (
19a–e). It is worth to note that excess of alkyl halides were used
for the preparation of series 1 compounds while only slight excess
(1.2 equiv) of alkyl halides were used for series 2 compounds.
anti-HIV activity of alkylated analogues of quinoline 2,4-diol based
on the natural products 1 and 2.
2. Results and discussion
2.1. Chemistry
The key intermediates quinoline 2,4-diol (3) and substituted
quinoline 2,4-diol (4) were synthesized18 in excellent yields by
condensation of aniline or substituted aniline and diethyl malonate
under microwave irradiation using 3–5 drops of DMF for 5–10 min
as outlined in Schemes 1 and 2. Synthesis of natural products 1 and
2 was achieved as reported in the literature.19,20 As shown in
Scheme 1, alkylation of 3 was performed by heating with K2CO3
and prenyl bromide in DMF at 60 °C to give natural product 2,
which underwent Claisen rearrangement when heated at 150 °C
in presence of N-methyl 2-pyrolidone (NMP) to form buchapine
(1) in 40% yield. To obtain potential anti-HIV agent, we designed
three series of compounds for synthesis.
2.1.3. Series 3
The hydroxyl groups at 2 and 4 positions of 3 or 4 were modi-
fied to investigate the role of these groups on anti-HIV activity.
The O-2,4-di-alkyl quinoline 2,4-diol analogues of 3 or 4 were syn-
thesized following the strategy shown in Scheme 4. The O-alkyl-
ation of 3 or 4 was done at 4-OH group by refluxing with alkyl
halides and K2CO3 in acetone to afford 20–29 in 60–80% yields.
Alkylation at 4-OH position was confirmed by 2D NMR study viz.
HMBC experiment; for example, in case of compound 24, methy-
lene protons (d 5.02) of propargyl moiety attached at 4-OH of quin-
oline 2,4-diol showed correlation with carbon at 4 position (d
161.51) as depicted in Figure 2. Subsequently, O-2 alkylation of
compounds 20–29 was accomplished by using similar reaction
condition with varying alkyl groups to yield compounds 30–47 in
50–70% yields (Scheme 4).
2.1.1. Series 1
Based on natural product 1, compounds 5–17 having dialkyl
substitutions on C-3 of 3 or 4 were synthesized as depicted in
Scheme 2. The C-3 di-alkylation of 3 or 4 was achieved in a single
Scheme 1. Reagents and conditions: (i) MW, 850 W, 3–5 drops DMF, 5–10 min, 95%; (ii) prenyl bromide, K2CO3, DMF, 60 °C, 12 h, 60%; (iii) N-methyl 2-pyrolidone, reflux, 2 h,
35%.
Scheme 2. Reagents and conditions: (i) MW, 850 W, 3–5 drops DMF, 5–10 min, 95–98%; (ii) LiOH, H2O, excess of RX0 (X0 = Br, 1), 80 °C, 24 h, 60–80%.
Scheme 3. Reagents and conditions: (i) RX, LiOH, H2O, 80 °C, 12 h, 50–70%; (ii) R1X, K2CO3, acetone, reflux, 12 h, 50–70%.

2874
N. Ahmed et al. / Bioorg. Med. Chem. 18 (2010) 2872–2879
Scheme 4. Reagents and conditions: (i) R1X, K2CO3, acetone, reflux, 12 h, 60–80%; (ii) R2X, K2CO3, acetone, reflux, 12 h, 50–70%.
exhibited good anti-HIV activity with 19a having IC50 value of
8.76 M. However, no compound had shown better activity than
l
2 indicating that prenyl group is best for HIV-1 inhibitory activity.
The chain lengths up to four carbons are required for activity. Ser-
Figure 2. Selected HMBC correlation of 24.
Table 1
Anti-HIV activity of synthesized compounds
2.2. Biological evaluation
T.I.e
c
d
Compounds Non-cytotoxic
% Inhibition
p24 ELISA
IC50
CC50
concn
lM
l
M
lM
CEM-GFP is a human CD4+ reporter T cell line, which expresses
GFP (green fluorescent protein) upon HIV infection due to trans-
activation by Tat protein of stably integrated long terminal repeat
regulated GFP gene. This cell line is used widely for determination
of anti-HIV activity due to easy visualization of infected cells.22
All synthesized analogues were first evaluated for their cytotox-
icity in MTT based cell viability assay23 in CEM-GFP cells. Further
non-cytotoxic concentration of each analogue was used for deter-
mination of in vitro anti-HIV activity in CEM-GFP cells. Out of var-
ious compounds tested, 13 derivatives have shown more than 60%
inhibition of HIV-1 replication as shown in Table 1. The lead natu-
ral product 1 was potent inhibitor of HIV-1 in our assay with IC50 of
1
2
5
6
23.51
20.20
31.12
8.41
24.48
—
80.09
87.52
44.3
96
74.65
N.S.b
82
2.99
3.80
N.D.a
2.35
16.73
—
55.89
71.17
—
62.62
113.46
—
67.38
—
103.38 11.80
191.72
160.13
146.83 12.65
77.37
—
18.69
18.72
—
26.64
6.78
—
7
8,19e,47
9
10–17,22
19a
19b
19c
19d
21
12.30
—
3.23
—
20.86
—
0
23.07
65.93
59.80
27.42
30.56
—
68.3
81.04
88.63
92.38
95.49
0
8.76
34.43
34.88
11.60
8.951
—
5.56
4.59
8.64
—
25–
2.99
thesized compounds 5–17. Compound 6 having prenyl substitution
is more potent than 1 with IC50 value of 2.35 M and has larger
CC50 of 62.6 M as compared to AZT (CC50 40 M). Compound 6
lM. Based on this background, we designed series 1 and syn-
29,33,35
23
24
30
31
43.29
35.17
1.84
1.68
1.59
76.74
65.06
23
31.2
15
3.89
19.34
—
—
—
114.67 29.47
102.51
—
—
—
5.3
—
—
—
—
l
l
l
has better therapeutic index (26.64) as compared to AZT (23.07).
The introduction of CH2 group to prenyl moiety led to reduction
32
38,40,41,46
—
0
—
—
34
36
37
39
42
43
44
45
AZT
23.36
22.30
21.20
12.30
14.98
16.73
18.58
19.60
4.98
47
35
16
32.68
2.56
16.08
56.4
56.4
89.75
N.D.
—
—
N.D.
—
—
N.D.
N.D.
1.04
N.D.
—
—
N.D.
—
—
N.D.
N.D.
24.0
—
—
—
—
—
—
—
—
in activity. Compound 9 showed IC50 value of 3.23 lM. Decrease
in length of alkyl chain to C-3, increase in length of alkyl chain to
C-6 or more caused decrease in activity (e.g., compounds 5 and 7
in Table 1). These results indicated that substitution by prenyl
group leads to compounds with better anti-HIV activity. To under-
stand the effect of substitution on ring B of quinoline 2,4-diol,
substituted derivatives 10–17 having chlorine and fluorine substi-
tution at different positions were tested. It is revealed from the
data in Table 1 that substitution on ring B led to complete loss of
anti-HIV activity. Thus unsubstituted ring B is essential for inhibi-
tion of HIV-1.
23.07
a
b
c
N.D. = not done.
N.S. = not soluble.
IC50 = concentration of compound required to achieve 50% protection of CEM-
GFP cells (n = 3) from virus, as determined by p24 ELISA assay.
d
Natural product 2 had shown potent inhibitory activity in our
CC50 = concentration of compound required to reduce proliferation of CEM-GFP
assay with IC50 value of 3.88
series 2 and synthesized various compounds. Among these, 19a–e
l
M. On this background, we designed
cells (n = 3) by 50%, as determined by MTT assay.
e
T.I. = therapeutic index.

N. Ahmed et al. / Bioorg. Med. Chem. 18 (2010) 2872–2879
2875
ies 1 and 2 indicated that C-3 di-substituted quinoline 2,4-dione
4.1.1. Synthesis of 3-(3-methylbut-2-enyl)-4-(3-methylbut-2-
derivatives are more potent than C-3, O-4 di-substituted quinoline
2,4-diol derivatives.
To determine the role of free hydroxyl groups, several O-mono
and O-dialkylated derivatives of quinoline 2,4-diol (series 3) were
evaluated. Among mono O-alkyl derivatives, few analogues (21, 23
and 24) had exhibited good activity. Compound 23 having isoamyl
enyloxy) quinolin-2-ol (2)
To a solution of 3 (200 mg, 1.25 mmol) in DMF (20 ml) and
potassium carbonate (1 g, 3.1 mmol) was added prenyl bromide
(0.33 ml, 3.1 mmol) at 30 °C and mixture was heated at 60 °C un-
der reflux for 12 h. The reaction mixture was cooled to 30 °C, di-
luted with water (10 ml) and extracted with ethyl acetate
(3 ꢀ 20 ml). The combined organic layer was washed with brine,
dried over MgSO4 and concentrated in vacuo to give crude product,
which was subjected to column chromatography (silica gel #60–
120, hexane/EtOAc-gradient) to afford 2 (220 mg, 60% yield) as
white solid. IR, 1H NMR and 13C NMR (CDCl3) data were consistent
with the literature.15 Anal. Calcd for C19H23NO2: C, 76.73; H, 7.80;
N, 4.71. Found: C, 76.87; H, 8.02; N, 4.76.
group on 4-OH showed IC50 value of 3.89
lM and CC50 of
114.67 M with best therapeutic index value of 29.47 amongst
l
all derivatives. Based on potent derivative 23, we synthesized ana-
logues 27–29. As shown in Table 1, a similar pattern to series 1 was
observed. The chloro and fluoro substitution on any of positions on
ring B of quinoline 2,4-diol led to loss of activity.
The potent inhibitors 21, 23 and 24 that possessed excellent to
good potency were chosen for further modification along with oth-
ers. Among O-dialkylated derivatives (30–47), none showed prom-
ising activity. It indicated that O-4 substituted quinoline 2,4-diol
derivatives possessed better activity than O-2,4 di-substituted
quinoline 2,4-diols. Further, free 2-OH of quinoline 2,4-diol is
essential for anti-HIV activity.
4.1.2. Synthesis of buchapine (1)
Compound 2 (100 mg, 0.33 mmol) was dissolved in N-methyl 2-
pyrrolidone (15 ml) and solution was refluxed at 150 °C for 2–3 h.
It was then diluted with water and extracted with ethyl acetate
(3 ꢀ 15 ml). The combined organic layer was dried over MgSO4
and concentrated in vacuo to give crude product which was sub-
jected to column chromatography (silica gel #60–120, hexane/
EtOAc-gradient) to afford 1 (35 mg, 35% yield) as light yellow solid.
1H NMR and 13C NMR (CDCl3) data were closely consistent with the
literature.15
3. Conclusion
In conclusion, 47 derivatives of quinoline 2,4-diol were synthe-
sized based on anti-HIV natural products 1 and 2 and evaluated for
in vitro anti-HIV activity in HIV-1NL4.3 infected CEM-GFP cells. The
structure activity relationship of quinoline 2,4-diol was studied for
anti-HIV activity. It indicated that the unsubstituted ring B and free
2-OH group are essential for anti-HIV activity. Further, the chain
length upto four carbons and prenyl group at C-3 and/or O-4 is re-
quired for HIV-1 inhibitory activity. The O-2,4-di-substituted quin-
oline 2,4-diols were inactive against HIV-1. The C-3-di-alkyl
quinoline 2,4-dione derivatives are more potent than C-3,O-4-di-
alkyl quinoline 2,4-diol derivatives. Moreover, this study led to
identification of potent inhibitors 6, 9 and 23. Compound 6 was
found to be more potent than lead molecule 1 with IC50 value of
4.2. General procedure for C-3 alkylation of 3
4.2.1. 3-Butylquinoline-2,4-diol (18b)
To a suspension of 3 (200 mg, 1.25 mmol) in water (20 ml) was
added lithium hydroxide (63 mg, 1.5 mmol) and stirred at 30 °C for
1 h. to give homogeneous solution. n-Butyl iodide (0.21 ml,
1.8 mmol) was added dropwise and reaction mixture was heated
at 80 °C under reflux for 12 h. Reaction mixture was cooled to
30 °C and extracted with ethyl acetate (3 ꢀ 30 ml). The combined
organic layer was washed with brine, dried over MgSO4 and con-
centrated in vacuo to give crude product, which upon column chro-
matography (silica gel #60–120, hexane/EtOAc-gradient) gave 18b
as white solid (200 mg, 73% yield). 1H NMR (300 MHz, CDCl3) d
0.79 (t, J = 6.3, 12.8 Hz, 3H), 1.10 (m, 2H), 1.24 (m, 2H), 2.2 (t,
J = 7.8, 14.8 Hz, 2H), 6.90 (d, J = 7.1 Hz, 1H), 7.17 (t, J = 7.1,
14.2 Hz, 1H), 7.59 (t, J = 7.7, 15.2 Hz, 1H), 7.91 (d, J = 7 Hz, 1H);
13C NMR (75.5 MHz, CDCl3) d 14, 22.3, 23.1, 33.8, 115.6, 118.2,
119.3, 124.3, 128.2, 132.1, 143.8, 175.8, 198.7; MS (APCI) m/z 218
[M+1]+; Anal. Calcd for C13H15NO2: C, 71.87; H, 6.96; N, 6.45.
Found: C, 71.23; H, 6.60; N, 6.39.
2.35 lM and had higher therapeutic index of 26.64 which was bet-
ter than AZT (23.07). The compound 23 showed best therapeutic
index value of 29.47 amongst all derivatives. Thus compounds 6
and 23 are safer than AZT. Few derivatives like 7, 19a, 19d, 21
and 24 were showed good inhibitory activity. All active compounds
showed higher CC50 values which indicate that they have broad
safety indices.
4. Experimental
4.1. Chemistry
4.3. General procedure for O-4 alkylation of 3-alkyl-quinoline
2,4-diol (18a–e)
All commercial chemicals and solvents are reagent grade and
were used without further treatment unless otherwise noted.
Nuclear magnetic resonance spectra were recorded on Brukers
avance (DPX 300 MHz) and (400 MHz) with tetramethyl silane
(TMS) as internal standard. Chemical shifts were recorded in
parts per million (ppm, d) and were reported relative to TMS.
Mass spectra were recorded on GCMS-QS Shimadzu (QP-500)
and LCMS waters (Micromass ZQ). IR spectra were recorded on
Nicolet spectrometer. The purity of samples was analysed by
HPLC (Waters INDIA Ltd) using C18 Merck column
(4.6 ꢀ 250 mm). Isocratic elution was carried out with mobile
phase as methanol/water (7:3). The combustion analyses were
carried out using Vario EL Elementar elemental analyzer. TLC
was performed on Merck 0.25 mm Kieselgel 60 F254 plates. Col-
umn chromatography was performed using either silica gel-60
(60–120 mesh). Details of %purity of compounds are available
as Supplementary data.
4.3.1. 4-Butoxy-3-butylquinolin-2-ol (19b)
To a suspension of 18b (100 mg, 0.4 mmol) in dried acetone
(10 ml) and K2CO3 (95 mg, 0.6 mmol) was added n-butyl iodide
(0.1 ml, 0.6 mmol) dropwise at 30 °C and reaction mixture was
then refluxed for 12 h. Reaction mixture was cooled to 30 °C and
filtered; filtrate was evaporated to dryness and the residue was
dissolved in ethyl acetate, washed with water (2x15 ml) and brine.
The organic layer was dried over MgSO4 and concentrated in vacuo
to give crude product, which upon column chromatography (silica
gel #60–120, hexane/EtOAc-gradient) gave 19b as white solid
(80 mg, 66% yield). 1H NMR (300 MHz, CDCl3) d 0.96 (t, J = 7.2,
16.3 Hz, 3H), 0.99 (t, J = 7.4, 13.8 Hz, 3H), 1.43 (q, J = 7.6, 15.7 Hz,
2H), 1.92 (q, J = 7.2, 14.6 Hz, 2H), 2.69 (t, J = 8.3, 17.2 Hz, 2H), 4.0
(t, J = 7.7, 15.6 Hz, 2H), 7.20 (t, J = 6.9, 14.6 Hz, 1H), 7.34 (d,
J = 9.2 Hz, 1H), 7.46 (t, J = 8.4, 18.1 Hz, 1H), 7.75 (d, J = 8.3 Hz,
1H); 13C NMR (75.5 MHz, CDCl3) d 14.5, 19.8, 20.8, 23.5, 24.9,

2876
N. Ahmed et al. / Bioorg. Med. Chem. 18 (2010) 2872–2879
30.3, 31.2, 31.5, 33, 68.8, 97.4, 114.6, 116.1, 121.8, 123.5, 130.3,
176.9; MS (APCI) m/z 204.1 [M+1]+; Anal. Calcd for C12H13NO2: C,
70.92; H, 6.45; N, 6.89. Found: C, 70.85; H, 6.49; N, 6.82.
137.7, 157.4, 163.9; MS (APCI) m/z 274 [M+1]+.
4.3.2. 3-(4-Methylpent-3-enyl)-4-(4-methylpent-3-enyloxy)
quinolin-2-ol (19a)
4.4.2. 4-(3-Methylbut-2-enyloxy) quinolin-2-ol (21)
White solid, 80% yield; IR (KBr, cmꢁ1): 3282, 2965, 2929, 1649,
1608, 1437, 1228; 1H NMR (300 MHz, CD3OD) d 1.81 (s, 3H), 1.84
(s, 3H), 4.27 (d, J = 7.3 Hz, 2H), 5.55 (t, J = 3.5, 8.2 Hz, 1H), 5.96 (s,
1H), 7.23 (t, J = 8.3, 16.4 Hz, 1H), 7.33 (d, J = 9.4 Hz, 1H), 7.54 (t,
J = 8.1, 16.2 Hz, 1H), 7.89 (d, J = 9.3 Hz, 1H); 13C NMR (75.5 MHz,
CD3OD) d 18.5, 24.3, 66, 96, 116.3, 119.1, 122.8, 123.4, 130.1,
137.3, 165.3, 177.1; MS (APCI) m/z 230.1 [M+1]+; Anal. Calcd for
C14H15NO2: C, 73.34; H, 6.59; N, 6.11. Found: C, 73.38; H, 6.56;
N, 5.78.
White solid, 72% yield; 1H NMR (300 MHz, CDCl3) d 1.62 (s, 3H),
1.66 (s, 3H), 1.70 (s, 3H), 1.76 (s, 3H), 2.36 (q, J = 7.4, 15.9 Hz, 2H),
2.59 (q, J = 7.5, 14.7 Hz, 2H), 2.73 (t, J = 8.2 Hz, 2H), 4.0 (t, J = 6.5,
13.2 Hz, 2H), 5.29 (m, 2H), 7.20 (t, J = 8.2, 19.3 Hz, 1H), 7.37 (d,
J = 10.4 Hz, 1H), 7.46 (t, J = 9.4, 23.4 Hz, 1H), 7.77 (d, J = 8.9 Hz,
1H); 13C NMR (75.5 MHz, CDCl3) d 18.2, 19.1, 22.4, 24.7, 28.3,
30.2, 69.4, 112.5, 116.1, 119.3, 120.9, 123.1, 127.4, 129.3, 135.4,
137.3, 163.2, 169.1; MS (APCI) m/z 326.1 [M+1]+; Anal. Calcd for
C21H27NO2: C, 77.50; H, 8.36; N, 4.30. Found: C, 77.63; H, 8.69;
N, 4.31.
4.4.3. 4-(Isopentyloxy) quinolin-2-ol (23)
Slight yellow solid, 80% yield; 1H NMR (300 MHz, CD3OD) d 1.01
(d, J = 6.4 Hz, 6H), 1.80 (q, J = 6.1, 13.4 Hz, 2H), 1.87 (m, 1H), 4.20 (t,
J = 6.9, 14.1 Hz, 2H), 5.96 (s, 1H), 7.24 (t, J = 7.6, 15.6 Hz, 1H), 7.31
(d, J = 7.9 Hz, 1H), 7.55 (t, J = 8.1, 15.9 Hz, 1H), 7.89 (d, J = 8.3 Hz,
1H); 13C NMR (75.5 MHz, CD3OD) d 22.2, 25.8, 37.8, 68.1, 96,
116.1, 122.9, 123.2, 131.9, 164.9, 176.2; MS (APCI) m/z 232
[M+1]+; Anal. Calcd for C14H17NO2: C, 72.70; H, 7.41; N, 6.06.
Found: C, 72.43; H, 7.69; N, 6.03.
4.3.3. 3-Isopentyl-4-(isopentyloxy)quinolin-2-ol (19c)
White solid, 60% yield; IR (KBr, cmꢁ1): 3436, 3168, 2930, 2872,
1650, 1610, 1466, 1369; 1H NMR (300 MHz, CDCl3) d 1.0 (t, J = 7.7,
15.2 Hz, 12H), 0.99 (t, J = 7.4 Hz, 3H), 1.55 (q, J = 7.4, 15.1 Hz, 2H),
1.71 (m, 1H), 1.81 (q, J = 7.7, 16.2 Hz, 2H), 1.93 (m, 1H), 2.70 (t,
J = 6.6, 13.6 Hz, 2H), 4.04 (t, J = 7.2, 15.2 Hz, 2H), 7.20 (t, J = 8.2,
19.5 Hz, 1H), 7.32 (d, J = 8.9 Hz, 1H), 7.47 (t, J = 8.7, 18.7 Hz, 1H),
7.72 (d, J = 9.1 Hz, 1H); 13C NMR (75.5 MHz, CDCl3) d 23.1, 23.4,
25.5, 29, 36.8, 38.3, 39.7, 73.7, 97.5, 114.5, 16.1, 118.1, 121.8,
122.6, 123.4, 124.5, 130.3, 137.7, 149.4, 163.4; MS (APCI) m/z 302
[M+1]+.
4.4.4. 4-(Prop-2-ynyloxy) quinolin-2-ol (24)
White solid, 75% yield; IR (KBr, cmꢁ1): 3436, 2925, 2840, 1650,
1608, 1498, 1411, 1260; 1H NMR (300 MHz, CDCl3) d 3.15 (s, 1H),
4.98 (s, 2H), 6.09 (s, 1H), 7.26 (t, J = 9.9, 19.2 Hz, 1H), 7.35 (d,
J = 11.1 Hz, 1H), 7.55 (t, J = 9.8, 20 Hz, 1H), 7.93 (d, J = 10.3 Hz,
1H); 13C NMR (75.5 MHz, CDCl3) d 57, 69.5, 74.4, 96.3, 114.5,
117.5, 121.6, 125.5, 134.5, 138.9, 170.5; MS (APCI) m/z 200
[M+1]+; Anal. Calcd for C12H9NO2: C, 72.35; H, 4.55; N, 7.03. Found:
C, 72.38; H, 4.60; N, 7.00.
4.3.4. 3-(Prop-2-ynyl)-4-(prop-2-ynyloxy)quinolin-2-ol (19d)
Slight yellow solid, 70% yield; IR (KBr, cmꢁ1): 3295, 2952, 2868,
1646, 1602, 1498, 1367, 1228; 1H NMR (300 MHz, CDCl3) d 2.02 (s,
1H), 2.63 (s, 1H), 3.7 (d, J = 2.6 Hz, 2H), 4.91 (d, J = 2.3 Hz, 2H), 7.41
(d, J = 9.2 Hz, 1H), 7.26 (t, J = 8.7, 15.7 Hz, 1H), 7.53 (t, J = 9.7,
18.1 Hz, 1H), 7.88 (d, J = 8.9 Hz, 1H); 13C NMR (75.5 MHz, CDCl3)
d 14.2, 57.3, 70.2, 76.3, 80.3, 81.1, 100.3, 116.5, 121.3, 122.9,
129.6, 138.5, 159.4, 161.7; MS (ESI) m/z 238 [M]+; Anal. Calcd for
C15H11NO2: C, 75.94; H, 4.67; N, 5.90. Found: C, 75.87; H, 4.70;
N, 5.88.
4.4.5. 4-(4-Methylpent-3-enyloxy) quinolin-2-ol (25)
White solid, 75% yield; 1H NMR (300 MHz, CD3OD) d 1.72 (s,
3H), 1.74 (s, 3H), 2.66 (q, J = 7.3, 14.2 Hz, 2H), 4.13 (t, J = 7.5,
15.1 Hz, 2H), 5.29 (t, J = 6.2, 12.5 Hz, 1H), 5.94 (s, 1H), 7.24 (t,
J = 8.3, 16.5 Hz, 1H), 7.31 (d, J = 9.3 Hz, 1H), 7.55 (t, J = 7.5,
15.6 Hz, 1H), 7.89 (d, J = 8.4 Hz, 1H); 13C NMR (75.5 MHz, CD3OD)
d 18.1, 23.9, 27.5, 65.4, 96.1, 116.4, 118,8, 122.3, 123.9, 130.7,
133.9, 165, 177.2; MS (APCI) m/z 244.1 [M+1]+; Anal. Calcd for
C15H17NO2: C, 74.05; H, 7.04; N, 5.76. Found: C, 73.98; H, 7.15;
N, 5.38.
4.3.5. 4-Isopropoxy-3-isopropylquinolin-2-ol (19e)
White solid, 58% yield; 1H NMR (300 MHz, CDCl3) d 1.38 (t,
J = 7.8, 14.9 Hz, 6H), 1.42 (t, J = 7.3, 15.1 Hz, 6H), 3.4 (m, 1H), 4.46
(m, 1H), 7.17 (m, 2H), 7.77 (d, J = 8.3 Hz, 1H), 7.41 (t, J = 8.6,
20.1 Hz, 1H); 13C NMR (75.5 MHz, CDCl3) d 22.3, 22.8, 23.5, 70.4,
99.2, 117.3, 120.5, 125, 128.1, 130.2, 139.1, 158, 163.8; MS (ESI)
m/z 245 [M]+.
4.4.6. 4-(2-Ethoxyethoxy) quinolin-2-ol (26)
Colourless oil, 65% yield; IR (KBr, cmꢁ1): 3392, 2974, 2868,
1650, 1608, 1503, 1436, 1405, 1232; 1H NMR (300 MHz, CDCl3) d
1.24 (t, 3H, J = 7.4, 14.2 Hz), 3.66 (q, 2H, J = 6.3, 12.1 Hz), 3.9 (t,
2H, J = 1.6, 3.1 Hz), 4.2 (t, 2H, J = 1.4, 2.9 Hz), 5.97 (s, 1H), 7.24 (t,
1H, J = 7.9, 15.8 Hz), 7.34 (d, 1H, J = 7.8 Hz), 7.54 (t, 1H, J = 8,
17.3 Hz), 7.98 (d, 1H, J = 7.4 Hz); 13C NMR (75.5 MHz, CDCl3,
ppm): d 16, 66.3, 69.1, 96.8, 114.2, 119.4, 121.2, 126.1, 131.3,
137.1, 159, 163.1; MS (APCI) m/z 234.1 [M+1]+; Anal. Calcd for
C13H15NO3: C, 66.94; H, 6.48; N, 6.00. Found: C, 66.81; H, 6.51;
N, 5.91.
4.4. General procedure for O-4 alkylation of 3 or 4
4.4.1. 4-Propoxyquinolin-2-ol (22)
To a suspension of 3 (100 mg, 0.6 mmol) in dried acetone
(15 ml) and K2CO3 (290 mg, 0.9 mmol) was added n-propyl bro-
mide (0.1 ml, 0.9 mmol) dropwise at 30 °C and reaction mixture
was then refluxed for 12 h. Reaction mixture was cooled to 30 °C
and filtered; filtrate was evaporated to dryness and the residue
was dissolved in ethyl acetate, washed with water (2x15 ml) and
brine. The organic layer was dried over MgSO4 and concentrated
in vacuo to give crude product, which upon column chromatogra-
phy (silica gel #60–120, hexane/EtOAc-gradient) gave 22 (100 mg,
79% yield). IR (KBr, cmꢁ1): 3435, 2964, 2840, 1642, 1611, 1376,
1227; 1H NMR (300 MHz, CD3OD) d 1.12 (t, J = 7.2, 14.7 Hz, 3H),
1.95 (m, 2H), 4.13 (t, J = 7.7, 15.1 Hz, 2H), 5.94 (s, 1H), 7.24 (t,
J = 8.1, 17.3 Hz, 1H), 7.34 (d, J = 9.3 Hz, 1H), 7.55 (t, J = 8.2,
17.9 Hz, 1H), 7.94 (d, J = 9.2 Hz, 1H); 13C NMR (75.5 MHz, CD3OD)
d 10.1, 22.5, 71, 96.2, 116.3, 122.5, 123.4, 127.1, 131.9, 165.3,
4.4.7. 7-Chloro-4-(isopentyloxy) quinolin-2-ol (27)
White solid, 78% yield; IR (KBr, cmꢁ1): 3363, 2954, 2900, 1677,
1592, 1528, 1419, 1169; 1H NMR (400 MHz, CDCl3) d 0.85 (d,
J = 6.8 Hz, 6H), 1.58 (q, J = 6.3, 10.3 Hz, 2H), 2.09 (m, 1H), 3.5 (t,
J = 6.1, 11.4 Hz, 2H), 6.21 (s, 1H), 7.14 (d, J = 7.4, 13.9 Hz, 1H),
7.43 (d, J = 7.6, 12.8 Hz, 1H), 7.8 (s, 1H), 9.2 (s, OH); 13C NMR
(100 MHz, CDCl3) d 22.2, 27.7, 31.8, 56.7, 96.3, 118.1, 120.3, 125,
30, 134.7, 138.3, 169.6, 180; MS (APCI) m/z 366 [M+1]+.

N. Ahmed et al. / Bioorg. Med. Chem. 18 (2010) 2872–2879
2877
4.4.8. 6-Fluoro-4-(isopentyloxy) quinolin-2-ol (28)
4.5.4. 2-Butoxy-4-(isopentyloxy) quinoline (33)
White solid, 73% yield; IR (KBr, cmꢁ1): 3269, 2958, 1673, 1618,
1507, 1406, 1215; 1H NMR (400 MHz, CDCl3) d 0.86 (d, J = 7.2 Hz,
6H), 1.57 (q, J = 5.3, 9.8 Hz, 2H), 2.09 (m, 1H), 3.34 (t, J = 6.3,
10.4 Hz, 2H), 6.31 (s, 1H), 7.01–7.07 (m, 2H), 7.55 (d, J = 5,6 Hz,
1H), 9.0 (s, OH); 13C NMR (100 MHz, CDCl3) d 22.3, 27.7, 31.6,
56.7, 97.3, 115.6, 115.8, 122, 122.1, 133.2, 133.3, 160.8, 169.4;
MS (APCI) m/z 250 [M+1]+.
White solid, 56% yield; 1H NMR (300 MHz, CDCl3) d 0.96 (d,
J = 2.2, 5 Hz, 6H), 1.0 (t, J = 1.9, 3.1 Hz, 3H), 1.46 (m, 2H), 1.66 (m,
2H), 1.75 (q, J = 4.8, 9.1 Hz, 2H), 1.87 (m, 1H), 4.11 (t, J = 7.4,
13.2 Hz, 2H), 4.27 (t, J = 7.1, 14.2 Hz, 2H), 6.01 (s, 1H), 7.20 (t,
J = 9.9, 19.3 Hz, 1H), 7.31 (d, J = 10.3 Hz, 1H), 7.55 (t, J = 10.1,
19.8 Hz, 1H), 7.99 (d, J = 11.6 Hz, 1H); 13C NMR (75.5 MHz, CDCl3)
d 13.8, 17.7, 20, 23.1, 25.9, 38.2, 51.3, 70, 97.7, 115.3, 117.4,
120.9, 124.9, 131.9, 138.2, 162.8; MS (APCI) m/z 288 [M+1]+.
4.4.9. 8-Fluoro-4-(isopentyloxy) quinolin-2-ol (29)
White solid, 75% yield; IR (KBr, cmꢁ1): 3264, 2952, 2866, 1678,
1595, 1531, 1451, 1261, 1162; 1H NMR (400 MHz, CDCl3) d 0.90 (d,
J = 6.4 Hz, 6H), 1.62 (q, J = 6.2, 11.3 Hz, 2H), 2.13 (m, 1H), 3.45 (t,
J = 6.3, 10.4 Hz, 2H), 6.23 (s, 1H), 7.09–7.17 (m, 2H), 8.24 (t,
J = 8.1, 18.2 Hz, 1H), 8.58 (s, OH); 13C NMR (100 MHz, CDCl3) d
22.3, 27.8, 31.4, 57.3, 97, 114.9, 115.1, 122.1, 124.5, 125, 125.6,
154, 169.7; MS (APCI) m/z 233 [M+1]+.
4.5.5. 2-(Benzyloxy)-4-(isopentyloxy) quinoline (34)
Colourless oil, 59% yield; 1H NMR (300 MHz, CDCl3) d 1.0 (d,
J = 34.1 Hz, 6H), 1.84 (q, J = 4.9, 9.6 Hz, 2H), 1.94 (m, 1H), 4.15 (t,
J = 6.3, 12.5 Hz, 2H), 5.52 (s, 2H), 6.11 (s, 1H), 7.21 (m, 7H), 7.45
(t, J = 10.2, 20.1 Hz, 1H), 7.99 (d, J = 10.6 Hz, 1H); 13C NMR
(75.5 MHz, CDCl3) d 22.7, 23.1, 37.2, 49.3, 68.4, 96.8, 115.1, 117.3,
120.3, 121.2, 121.9, 125.9, 129.9, 139.2, 164.1; MS (APCI) m/z 322
[M+1]+.
4.5. General procedure for O-2 alkylation of O-4 alkyl 2,4-
dihydroxy quinoline (20–29)
4.5.6. 2,4-Bis(3-methylbut-2-enyloxy) quinoline (35)
White solid, 67% yield; IR (KBr, cmꢁ1): 3459, 2970, 2914, 1645,
1591, 1498, 1455,1378; 1H NMR (300 MHz, CDCl3) d 1.65 (s, 3H),
1.71 (s, 3H), 1.82 (s, 3H), 1.87 (s, 3H), 4.62 (d, J = 7.4 Hz, 2H), 4.88
(d, J = 7.3 Hz, 2H), 5.11 (t, J = 5.4, 9.4 Hz, 1H), 5.53 (t, J = 5.8,
11 Hz, 1H), 6.03 (s, 1H), 7.19 (t, J = 8.1, 17 Hz, 1H), 7.22 (d,
J = 10.2 Hz, 1H), 7.53 (t, J = 9.3, 17.3 Hz, 1H), 8.01 (d, J = 9.8 Hz,
1H); 13C NMR (75.5 MHz, CDCl3) d 18.8, 26.1, 26.3, 40.9, 66, 97.7,
115, 118.8, 120.5, 121.8, 124.1, 131.4, 136, 139.7, 164.1, 166.5;
MS (APCI) m/z 298 [M+1]+; Anal. Calcd for C19H23NO2: C, 76.73;
H, 7.80; N, 4.71. Found: C, 76.67; H, 8.00; N, 4.71.
4.5.1. 2-(Allyloxy)-4-(isopentyloxy) quinoline (30)
To a suspension of 20 (100 mg, 0.4 mmol) in dried acetone
(10 ml) and K2CO3 (200 mg, 0.6 mmol) was added allyl bromide
(0.05 ml, 0.6 mmol) dropwise at 30 °C and mixture was then re-
fluxed for 12 h. Reaction mixture was cooled to 30 °C and fil-
tered; filtrate was evaporated to dryness and the residue was
dissolved in ethyl acetate, washed with water (2 ꢀ 20 ml) and
brine. The organic layer was dried over MgSO4 and concentrated
in vacuo to give crude product, which upon column chromatog-
raphy (silica gel #60–120, hexane/EtOAc-gradient) gave 30 as
white solid (75 mg, 65% yield). 1H NMR (300 MHz, CD3OD) d
1.01 (d, J = 6.3 Hz, 6H), 1.78 (q, J = 6.7, 13.1 Hz, 2H), 1.9 (m,
1H), 4.12 (t, J = 6.9 Hz, 2H), 4.90 (d, J = 7.1 Hz, 2H), 5.04 (dd,
J = 0.7, 16.2 Hz, 1H), 5.17 (dd, J = 0.8, 14.7 Hz, 1H), 5.90 (m, 1H),
6.04 (s, 1H), 7.20 (t, J = 8.2, 16.7 Hz, 1H), 7.26 (d, J = 9.2 Hz, 1H),
7.55 (t, J = 8.4, 17 Hz, 1H), 7.97 (d, J = 9.9 Hz, 1H); 13C NMR
(75.5 MHz, CD3OD) d 23.1, 24.4, 39.4, 66.1, 71.7, 96.2, 117.9,
118.5, 122.1, 123.8, 130.2, 133.5, 138, 163.6, 164.9; MS (APCI)
m/z 272 [M+1]+.
4.5.7. 2-(Allyloxy)-4-(3-methylbut-2-enyloxy) quinoline (36)
Light yellow solid, 63% yield; 1H NMR (300 MHz, CDCl3) d 1.76
(s, 3H), 1.82 (s, 3H), 4.62 (d, J = 6.6 Hz, 2H), 4.91 (t, J = 2.6, 5.1 Hz,
2H), 5.10 (dd, J = 0.3, 17.2 Hz, 1H), 5.20 (dd, J = 0.3, 16.8 Hz, 1H),
5.53 (t, J = 5.7, 11.9 Hz, 1H), 5.92 (m, 1H), 6.05 (s, 1H), 7.18 (t,
J = 8.3, 17.5 Hz, 1H), 7.28 (d, J = 10.2 Hz, 1H), 7.51 (t, J = 9,
19.1 Hz, 1H), 7.99 (d, J = 11.4 Hz, 1H); 13C NMR (75.5 MHz, CDCl3)
d 18.3, 23.9, 66.7, 71.2, 97.6, 116.2, 119.5, 122.8, 123.8, 130.3,
138.9, 162.7, 164.9; MS (APCI) m/z 270.1 [M+1]+.
4.5.8. 2-(Allyloxy)-4-(4-methylpent-3-enyloxy) quinoline (37)
White solid, 69% yield; 1H NMR (300 MHz, CDCl3) d 1.61 (s, 3H),
1.64 (s, 3H), 2.60 (q, J = 4.7, 9.2 Hz, 2H), 4.23 (t, J = 5.3, 11.4 Hz, 2H),
4.91 (t, J = 3.2, 6.4 Hz, 2H), 5.04 (dd, J = 0.2, 19.2 Hz, 1H), 5.17 (dd,
J = 0.2, 20 Hz, 1H), 5.26 (m, 1H), 5.91 (m, 1H), 6.03 (s, 1H), 7.20 (t,
J = 7.9, 15.5 Hz, 1H), 7.29 (d, J = 9.3 Hz, 1H), 7.53 (t, J = 8.1, 16 Hz,
1H), 8.0 (d, J = 9.7 Hz, 1H); 13C NMR (75.5 MHz, CDCl3) d 14.7,
28.2, 30.2, 44.6, 60.9, 68.8, 97.3, 115.2, 117.1, 119.5, 122.1, 123.9,
131.9, 132.7, 159.8, 163.2; MS (APCI) m/z 284.4 [M+1]+.
4.5.2. 4-(Isopentyloxy)-2-(3-methylbut-2-enyloxy) quinoline
(31)
White solid, 70% yield; 1H NMR (300 MHz, CD3OD) d 1.0 (d,
J = 6.4 Hz, 6H), 1.71 (s, 3H), 1.87 (s, 3H), 1.79 (q, J = 6.1,
12.7 Hz, 2H), 1.92 (m, 1H), 4.11 (t, J = 6.7 Hz, 2H), 4.90 (d,
J = 6.7 Hz, 2H), 5.12 (t, J = 1.7, 3.2 Hz, 1H), 6.02 (s, 1H), 7.19 (t,
J = 8.4, 17 Hz, 1H), 7.28 (d, J = 9.2 Hz, 1H), 7.53 (t, J = 8.6,
17.2 Hz, 1H), 7.98 (d, J = 9.4 Hz, 1H); 13C NMR (75.5 MHz, CD3OD)
d 18.2, 23.2, 24.2, 38.6, 66, 69.4, 97.2, 117.5, 118.3, 122, 123.4,
130.7, 139, 164.6, 165; MS (APCI) m/z 200 [M+1]+; Anal. Calcd
for C19H25NO2: C, 76.22; H, 8.42; N, 4.68. Found: C, 76.54; H,
8.70; N, 4.63.
4.5.9. 2-(3-Methylbut-2-enyloxy)-4-(4-methylpent-3-enyloxy)
quinoline (38)
White solid, 70% yield; 1H NMR (300 MHz, CDCl3) d 1.70 (s, 3H),
1.74 (s, 3H), 2.59 (q, J = 4.9, 9.7 Hz, 2H), 4.04 (t, J = 6.8, 13.4 Hz, 2H),
4.88 (t, J = 5.1, 11.2 Hz, 2H), 5.12 (t, J = 5.9, 12.2 Hz, 1H), 5.23 (t,
J = 7.2, 13.2 Hz, 1H), 6.01 (s, 1H), 7.20 (t, J = 8.9, 17.5 Hz, 1H), 7.28
(d, J = 10.2 Hz, 1H), 7.53 (t, J = 8.3, 17.7 Hz, 1H), 7.99 (d,
J = 10.4 Hz, 1H); 13C NMR (75.5 MHz, CDCl3) d 18.4, 18.8, 22.8,
23.8, 26.2, 40.9, 68.5, 97.4, 115, 119.6, 120.5, 121.9, 132.9, 124,
131.4, 136, 139.7, 164.1; MS (APCI) m/z 312.3 [M+1]+.
4.5.3. 4-(Isopentyloxy)-2-(4-methylpent-3-enyloxy) quinoline
(32)
White solid, 65% yield; 1H NMR (300 MHz, CDCl3) d 1.0 (d,
J = 6.5 Hz, 6H), 1.60 (s, 3H), 1.62 (s, 3H), 1.82 (q, J = 6.8, 14 Hz,
2H), 1.92 (m, 1H), 2.39 (q, J = 6.3, 13.1 Hz, 2H), 4.11 (t, J = 6.9,
13.9 Hz, 2H), 4.21 (t, J = 7.1, 14.4 Hz, 2H), 5.24 (t, J = 6.8, 13.5 Hz,
1H), 6.01 (s, 1H), 7.20 (t, J = 8.5, 17.1 Hz, 1H), 7.36 (d, J = 9.5 Hz,
1H), 7.55 (t, J = 8.2, 16.6 Hz, 1H), 7.99 (d, J = 9.6 Hz, 1H); 13C NMR
(75.5 MHz, CDCl3) d 18.1, 22.8, 23.2, 28.1, 37.6, 66.4, 70.3, 96.4,
116.4, 121.6, 123.8, 127.5, 130.9, 133.7, 163.8, 165.1; MS (APCI)
m/z 314.5 [M+1]+.
4.5.10. 2,4-Bis(4-methylpent-3-enyloxy) quinoline (39)
White solid, 68% yield; 1H NMR (300 MHz, CDCl3) d 1.59 (s, 6H),
1.62 (s, 6H), 2.23 (m, 4H), 4.07 (t, J = 7.1, 14.3 Hz, 2H), 4.25 (t,
J = 6.8, 12.5 Hz, 2H), 5.01 (t, J = 5.4, 11.9 Hz, 1H), 5.23 (t, J = 6.2,

2878
N. Ahmed et al. / Bioorg. Med. Chem. 18 (2010) 2872–2879
12.2 Hz, 1H), 6.0 (s, 1H), 7.20 (t, J = 8.4, 17.2 Hz, 1H), 7.36 (d,
J = 11 Hz, 1H), 7.54 (t, J = 9.2, 18 Hz, 1H), 7.97 (d, J = 11.7 Hz, 1H);
13C NMR (75.5 MHz, CDCl3) d 18.2, 18.6, 22.2, 22.9, 26.3, 39.9,
67.9, 97.2, 115.2, 117.3 119.2, 121.5, 121.9, 133.9, 124.8, 132.5,
139.3, 139.7, 163.1; MS (ESI) m/z 325 [M]+; Anal. Calcd for
C21H27NO2: C, 77.50; H, 8.36; N, 4.30. Found: C, 77.28; H, 8.25;
N, 4.29.
4.5.16. 2-Butoxy-4-(prop-2-ynyloxy) quinoline (45)
White solid, 53% yield; 1H NMR (300 MHz, CDCl3) d 1.0 (d,
J = 6.4 Hz, 3H), 1.43 (m, 2H), 1.79 (m, 2H), 2.58 (s, 1H), 4.20 (t,
J = 6.1, 12.7, 2H), 4.73 (t, J = 6.5, 12.1 Hz, 2H), 6.0 (s, 1H), 7.20 (t,
J = 6.2, 14.1 Hz, 1H), 7.34 (d, J = 5.2 Hz, 1H), 7.54 (t, J = 7.1,
14.3 Hz, 1H), 8.01 (d, J = 7.4 Hz, 1H); 13C NMR (75.5 MHz, CDCl3)
d 14.3, 19.9, 30.2, 56.4, 69, 75.2, 97, 116.2, 121, 126.1, 130.3,
139.2, 160, 162.6; MS (APCI): m/z 256.1 [M+1]+; Anal. Calcd for
C16H17NO2: C, 75.27; H, 6.71; N, 5.49. Found: C, 75.53; H, 6.89;
N, 5.52.
4.5.11. 2-Butoxy-4-(4-methylpent-3-enyloxy) quinoline (40)
Light yellow solid, 53% yield; IR (KBr, cmꢁ1): 3364, 2984, 2868,
1663, 1591, 1488, 1401, 1222; 1H NMR (300 MHz, CDCl3) d 0.98 (t,
J = 7.4, 14.1 Hz, 3H), 1.70 (s, 3H), 1.74 (s, 3H), 1.43 (m, 2H), 2.0 (m,
2H), 2.59 (q, J = 5.2, 10.1 Hz, 2H), 4.04 (t, J = 6.3, 11.9 Hz, 2H), 4.27
(t, J = 6.9, 13.1 Hz, 2H), 5.23 (t, J = 7.1, 13.3 Hz, 1H), 6.0 (s, 1H), 7.23
(t, J = 9.2, 18.2 Hz, 1H), 7.34 (d, J = 10.1 Hz, 1H), 7.56 (t, J = 9.8,
18.2 Hz, 1H), 8.0 (d, J = 11.4 Hz, 1H); 13C NMR (75.5 MHz, CDCl3)
d 14.2, 18.2, 19.3, 22.2, 26.9, 34.3, 65.9, 69.4, 97.6, 116.1, 117.7,
121.5, 122.3, 124.2, 130.9, 135.5, 138.1, 163.1; MS (APCI) m/z 300
[M+1]+.
4.5.17. 2,4-Bis(2-ethoxyethoxy) quinoline (46)
Colourless oil, 67% yield; 1H NMR (300 MHz, CDCl3) d 1.21 (t,
J = 6, 11.9 Hz, 3H), 1.28 (t, J = 5.7, 10.9 Hz, 3H), 3.66 (q, J = 6.3,
14.1 Hz, 4H), 3.83 (t, J = 4.8, 9.2 Hz, 2H), 3.91 (t, J = 4.5, 9.7 Hz,
2H), 4.27 (t, J = 6.3, 13.1 Hz, 2H), 4.63 (t, J = 5.9, 10.6 Hz, 2H), 6.29
(s, 1H), 7.32 (t, J = 7.4, 15.1 Hz, 1H), 7.55 (d, J = 7.3 Hz, 1H), 7.75
(t, J = 6.9, 14.8 Hz, 1H), 8.10 (d, J = 7.7 Hz, 1H); 13C NMR
(75.5 MHz, CDCl3) d 15.7, 65.5, 67.1, 68.5, 69, 69.5, 92.2, 122.5,
123.7, 127.3, 130.4, 163.2; MS (APCI) m/z 304 [Mꢁ1]+.
4.5.12. 2-(Benzyloxy)-4-(4-methylpent-3-enyloxy) quinoline
(41)
4.5.18. 2,4-Bis(octyloxy) quinoline (47)
Colourless oil, 55% yield; IR (KBr, cmꢁ1): 3262, 2898, 1632,
1535, 1348, 1270, 1143; 1H NMR (300 MHz, CDCl3) d 1.71 (s, 3H),
1.75 (s, 3H), 2.66 (q, J = 5.4, 11 Hz, 2H), 4.08 (t, J = 7.3, 13.6 Hz,
2H), 5.25 (t, J = 7.3, 14.3 Hz, 1H), 5.5 (s, 2H), 6.10 (s, 1H), 7.12 (m,
6H), 7.29 (d, J = 9.3 Hz, 1H), 7.40 (t, J = 9.9, 18.9 Hz, 1H), 7.96 (d,
J = 11.2 Hz, 1H); 13C NMR (75.5 MHz, CDCl3) d 18.7, 22.1, 27.3,
51.3, 68.3, 97, 116.3, 117.1, 120.1, 121.4, 124.9, 131.9, 136.3,
137.2, 165.8; MS (APCI) m/z 334 [M+1]+.
Colourless oil, 72% yield; IR (KBr, cmꢁ1): 3436, 2953, 2953,
2855, 1647, 1591, 1455,1230; 1H NMR (300 MHz, CDCl3) d 0.88
(t, J = 4.2 Hz, 6H), 1.28 (m, 20H), 1.69 (q, J = 5.2, 9.5 Hz, 2H), 1.90
(q, J = 5.3, 10.1, 2H), 4.07 (t, J = 6.1, 12.6 Hz, 2H), 4.23 (t, J = 6.9,
11.9 Hz, 2H), 6.0 (s, 1H), 7.20 (t, J = 5.9, 10.9 Hz, 1H), 7.31 (d,
J = 7.1 Hz, 1H), 7.56 (t, J = 7.2, 13.3 Hz, 1H), 8.0 (d, J = 6.2 Hz, 1H);
13C NMR (75.5 MHz, CDCl3) d 14.6, 23.1, 26.6, 27.5, 28.2, 28.7,
29.2, 29.8, 29.9, 32.3, 33.3, 34.6, 42.4, 69.1, 97.4, 114.6, 117.4,
121.8, 124, 131.5, 139.5, 162.3, 164.2; MS (APCI) m/z 384 [M+1]+;
Anal. Calcd for C25H39NO2: C, 77.87; H, 10.19; N, 3.63. Found: C,
77.76; H, 10.25; N, 3.65.
4.5.13. 2-(3-Methylbut-2-enyloxy)-4-(prop-2-ynyloxy)
quinoline (42)
White solid, 64% yield; IR (KBr, cmꢁ1): 3322, 2945, 2811, 2319,
1611, 1549, 1412, 1302; 1H NMR (300 MHz, CDCl3) d 1.71 (s, 3H),
1.81 (s, 3H), 2.6 (s, 1H), 4.82 (s, 2H), 4.91 (d, J = 6.5 Hz, 2H), 5.13
(t, J = 1.2, 3.3 Hz, 1H), 6.15 (s, 1H), 7.21 (t, J = 7.9, 15.2 Hz, 1H),
7.30 (d, J = 8 Hz, 1H), 7.55 (t, J = 9.3, 18.4 Hz, 1H), 8.0 (d,
J = 9.2 Hz, 1H); 13C NMR (75.5 MHz, CDCl3) d 18.3, 24.1, 57.2,
69.2, 75.4, 97.3, 114.5, 117.5, 121.6, 125.5, 130.4, 132.2, 134.3,
136.9, 169.5; MS (APCI) m/z 268.1 [M+1]+; Anal. Calcd for
C17H17NO2: C, 76.38; H, 6.41; N, 5.24. Found: C, 76.66; H, 6.26;
N, 5.27.
4.6. Biological methods
4.6.1. Cell cytotoxicity assay using MTT
The synthesized analogues were tested for their cytotoxicity in
cell viability assay and non-toxic concentration of each analogue
was used for further screening in cell based anti-HIV assay. The
cytotoxicity was assessed by using MTT based cell viability assay
Kit (Roche, Germany) in the CEM-GFP, according to the manufac-
turer’s protocol. Briefly, 2 ꢀ 104 cells/well were seeded in 96-well
plate; samples were then added into the wells at different concen-
trations keeping untreated wells as controls. After 48–72 h incuba-
4.5.14. 2-(Allyloxy)-4-(prop-2-ynyloxy) quinoline (43)
White solid, 71% yield; IR (KBr, cmꢁ1): 3233, 2991, 2858, 2396,
1710, 1599, 1470, 1305, 1200; 1H NMR (300 MHz, CDCl3) d 2.61 (s,
1H), 4.83 (s, 2H), 4.93 (d, J = 6.4 Hz, 2H), 5.11 (dd, J = 1.2, 10.5 Hz,
1H), 5.22 (dd, J = 1.3, 9.2 Hz, 1H), 5.92, (m, 1H), 6.15 (s, 1H), 7.22
(t, J = 8.9, 17.2 Hz, 1H), 7.28 (d, J = 8.6 Hz, 1H), 7.54 (t, J = 8.2,
18.6 Hz, 1H), 8.01 (d, J = 7.8 Hz, 1H); 13C NMR (75.5 MHz, CDCl3)
d 57.3, 70.5, 74.1, 97.1, 114.4, 115.5, 119.6, 125.5, 131.9, 134.0,
137.4, 169.9; MS (APCI) m/z 240.1 [M+1]+; Anal. Calcd for
C15H13NO2: C, 75.30; H, 5.48; N, 5.85. Found: C, 75.71; H, 5.56;
N, 5.81.
tion, 10 ll of MTT Reagent (5 mg/ml) were added into the wells to
allow the reaction to proceed. Formazan crystals produced during
the reaction were solubilized and colour development was read at
540 nm.
4.6.2. Anti HIV screening in CEM-GFP cells
Human CD4+ T cell line, CEM-GFP cells were infected with HIV-
1NL-4.3 virus at a multiplicity of infection (MOI) of 0.05 using the
standard protocol previously published from our laboratory.24
The cells were then incubated with samples for up to 8 days post
infection. Virus production was assayed in the culture supernatant
on day 8 post infection by p24 antigen capture ELISA (Perkin–El-
mer, USA).
4.5.15. 2-(Isopentyloxy)-4-(prop-2-ynyloxy) quinoline (44)
White solid, 61% yield; 1H NMR (300 MHz, CDCl3) d 1.02 (s, 3H),
1.04 (s, 3H), 1.61 (q, J = 5.8, 12.5 Hz, 2H), 1.87 (m, 1H), 2.61 (s, 1H),
4.26 (t, J = 7.2, 13.7 Hz, 2H), 4.82 (s, 2H), 6.13 (s, 1H), 7.21 (t, J = 6.0,
14.3 Hz, 1H), 7.31 (d, J = 5.8 Hz, 1H), 7.58 (t, J = 6.7, 13.9 Hz, 1H), 8.0
(d, J = 7.3 Hz, 1H); 13C NMR (75.5 MHz, CDCl3) d 23.1, 27, 30.2, 36,
56.8, 98.5, 114.5, 122, 124.1, 131.8, 139.5, 160.9, 163.6; MS (APCI)
m/z 270.1 [M+1]+; Anal. Calcd for C17H19NO2: C, 75.81; H, 7.11; N,
5.20. Found: C, 75.98; H, 7.29; N, 5.24.
Acknowledgement
Authors thank the Department of Biotechnology, Ministry of
Science and Technology, Government of India for the financial sup-
port to this project (Grant No. BT/PR7020/Med/14/930/2005 Dt.
23/05/2006).

N. Ahmed et al. / Bioorg. Med. Chem. 18 (2010) 2872–2879
2879
10. Manfredi, K. P.; Blunt, J. W.; Cardellina, J. H. I.; McMahon, J. B.; Pannell, L. K.;
Cragg, G. M.; Boyd, M. R. J. Med. Chem. 1991, 34, 3402.
11. Kim, H. J.; Yu, Y. G.; Park, H.; Lee, Y. S. Planta Med. 2002, 68, 1034.
12. Nakane, H.; Arisawa, M.; Fujita, A.; Koshimura, S.; Ono, K. FEBS Lett. 1991, 286,
83.
13. Nishizawa, M.; Emura, M.; Kan, Y.; Yamada, H.; Ogawa, K.; Hamanaka, N.
Tetrahedron Lett. 1992, 33, 2983.
14. Nesmelova, E. F.; Bessonova, I. A.; Yu. Yunusov, S. Y. Khim. Prir. Soedin. 1982, 4,
532.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmc.2010.03.015.
References and notes
15. Giuma, M. S.; Karima, A.; Bahlul, Z. E.; Aziza, S. A.; Fatma, A. A.; Hala, H. A.
Phytochemistry 1987, 26, 3339.
16. McCormick, J. L.; McKee, T. C.; Cardellina, J. H.; Boyd, M. R. J. Nat. Prod. 1996, 59,
469.
17. Brahmbhatt, K. G.; Nafees, A.; Singh, I. P.; Bhutani, K. K. Tetrahedron Lett. 2009,
50, 5501.
18. Kapil, A.; Agarwal, M. Bioorg. Med. Chem. Lett. 2007, 17, 86.
19. Michael, F. G.; Ramachandran, V. N. Tetrahedron Lett. 1985, 26, 4253.
20. Aurora, B.; Pietro, V. Heterocycles 1986, 24, 1821.
21. Nafees, A.; Brahmbhatt, K. G.; Singh, I. P.; Bhutani, K. K. J. Heterocycl. Chem.
2010, doi:10.1002/jhet.364.
22. Ladha, J. S.; Tripathy, M. K.; Mitra, D. Cell Death Differ. 2005, 12, 1417.
23. Denizot, F.; Rita, L. J. Immunol. Methods 1989, 89, 271.
24. Kumar, M.; Mitra, D. J. Biol. Chem. 2005, 280, 40041.
1. AIDS Epidemic Update UNAIDS (http://www.unaids.org) 2009.
2. Oxenius, A.; Fidler, S.; Brady, M.; Dawson, J.; Ruth, K.; Easterbook, P. J.; Weber, J.
N.; Philips, R. E.; Price, D. A. Eur. J. Immunol. 2001, 31, 3782.
3. Ma, C. M.; Nakamura, N.; Miyashiro, H.; Hattori, M.; Komatsu, K.; Kawahata, T.;
Otake, T. Phytother. Res. 2002, 16, 186.
4. Yves, P.; Allison, A. J.; Christophe, M. Nat. Rev. Drug Disc. 2005, 4, 236.
5. Butler, M. S. Nat. Prod. Rep. 2008, 25, 475.
6. Singh, I. P.; Bharate, S. B.; Bhutani, K. K. Curr. Sci. 2005, 89, 269.
7. Kashiwada, Y.; Hashimoto, F.; Cosentino, L. M.; Chen, C. H.; Garrett, P. E.; Lee, K.
H. J. Med. Chem. 1996, 39, 1016.
8. Patil, A. D.; Kumar, N. V.; Kokke, W. C.; Bean, M. F.; Freyer, A. J.; Brosse, C. D.;
Mai, S.; Truneh, A.; Carte, B. J. Org. Chem. 1995, 60, 1182.
9. Ishida, J.; Wang, H. K.; Oyama, M.; Cosentino, M. L.; Hu, C. Q.; Lee, K. H. J. Nat.
Prod. 2001, 64, 958.